1. Field of the Invention
The present invention relates to microcircuit probes. More particularly, the present invention relates to an improved microcircuit probe and a method for its manufacture.
2. The Prior Art
After the manufacture of microcircuits it is typical that they be electrically tested prior to delivery as a finished product. As microcircuits have become more complex the associated electrical testing has also become more complex and expensive. It is desirable that the microcircuit be tested for electrical functionality even prior to the permanent application of terminal leads to the product. Prior to this permanent application of terminal leads, the electrically conductive probe is the means by which elements of macroscopic test equipment contact microscopic circuit elements. Because of the microscopic size of the area of electrical contact on a microcircuit it is critical to maintain tight dimensional control over any element which makes physical contact with such an area.
Present microcircuit probes are generally circular in cross section and are generally made by nickel plating a one inch long piece of 0.010" diameter wire, usually made of tungsten. One end of the wire about 0.200" long is electrochemically etched into a point and a bend about 0.020" long is made at a precise angle with the rest of the wire. The tip is then sanded to reach a final tip length of about 0.007" and cross section of about 0.002".
The probe tips of the prior art present several problems. First, the process of manufacturing the probe is time consuming, occasionally inaccurate, resulting in scrap.
In addition, in order for the probe tip to achieve the correct force on the microcircuit pad, it is necessary for the diameter of the probe to be at least 0.010". This presents a limitation as to how closely together probes can be placed before electrical interference occurs, or probes physically touch. Current microcircuit pad spacings are about 0.008" center to center.
As probes are used, wear occurs and the probe tip becomes shorter and the diameter of the contact area of the tip increases, due to the taper. As the tip diameter increases, the pressure that the tip exerts on the microcircuit pad decreases, eventually resulting in poor electrical contact.
Furthermore, probes must occasionally be replaced after they have been in use. This is difficult with current technology because the non-tapered end of the replacement probe does not always easily fit back into the hole from which the original probe was removed. This problem is further complicated by the fact that probes having circular cross sections are not easily handled with tweezers.
Accordingly, it is one object of the present invention to provide a higher quality and more cost effective probe having special utility to effect temporary electrical connection between a microcircuit and electrical test equipment. It is another object of the invention to provide a novel method of manufacturing this electrically conductive probe in such a manner as to guarantee its higher quality and cost effectiveness.